What’s the connection between car parks and climate change? Each year shoppers in the UK drive a combined nine billion kilometres to stores to do their food shopping, generating around three million tonnes of CO2.

To put it in context, that’s the equivalent of the carbon footprint of the entire country of Nepal.

Why oh why then do we have so many huge supermarket car parks? On the face of it, the logic for retailers is pretty clear. They think customers need a car parked close by so they can take away as much shopping as possible.

And this appears to be borne out by the numbers. Drivers take away an estimated five-and-a-half times more products than non-drivers. A survey from a couple of years ago showed that 86% of those who have shopping responsibility (and who drive) usually take a car to the supermarket to do their weekly shop. So car parks are arguably one of the things that enable the "pile 'em high, sell 'em cheap and drive 'em home" supermarket model to function.

It’s not the humble car park’s fault on its own, I accept. But surely this is a self-fulfilling prophecy? People are encouraged to drive to store because there is somewhere convenient to park. And parking spaces are provided because people are driving there.

If you look at it from a different perspective – quite literally - from the air, then car parks seem less logical. They are often bigger than the retail outlets themselves – surely not the most economically efficient use of the retailer’s land? There must be a financial case for retailers to sell off part of that (often very valuable) land, or simply for them to share use during non-busy times.

I’m not suggesting that retailers get rid of all their car parks – that’s not realistic. But I do believe that they can reduce the number of customer trips (and hence the number of parking spaces required) without reducing their overall customer base.

What does that mean in practice? Simple – retailers should follow our standard travel hierarchy.

Enable shoppers to avoid the journey to store, e.g. by making online shopping easier and more attractive, as Waitrose did recently by scrapping their delivery charge for online grocery shopping.

Encourage drivers to reduce the total number of journeys, e.g. by combining shopping trips.

And help customers switch to lower-carbon alternative travel options, e.g. work with local authorities to make sure stores are served by public transport networks and, in the longer-term, give customers incentives to use electric or hybrid cars.

More fundamentally, retailers should strive to reduce the packaging and weight of the products they sell (e.g. by using concentrates). Of the many benefits this would have, one would be to make people’s shopping bags smaller, thus enabling them to be carried on public transport more easily.

So, my take-home message to retailers: let’s find creative ways of providing low-carbon customer access to your products and services, and let’s give the car parking space the opportunity of a change of career.

This ‘driving to store’ blog is the first in a series about notable but neglected retail impacts.